Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation

ABSTRACT Melanins are biopolymers that confer coloration and protection to the host organism against biotic or abiotic insults. The level of protection offered by melanin depends on its biosynthesis and its subcellular localization. Previously, we discovered that Aspergillus fumigatus compartmentali...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Srijana Upadhyay, Xinping Xu, Xiaorong Lin
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2016
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/8bd9292c7398484781d81a7e3526b605
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:8bd9292c7398484781d81a7e3526b605
record_format	dspace
spelling	oai:doaj.org-article:8bd9292c7398484781d81a7e3526b6052021-11-15T15:50:15ZInteractions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation10.1128/mBio.01925-162150-7511https://doaj.org/article/8bd9292c7398484781d81a7e3526b6052016-12-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01925-16https://doaj.org/toc/2150-7511ABSTRACT Melanins are biopolymers that confer coloration and protection to the host organism against biotic or abiotic insults. The level of protection offered by melanin depends on its biosynthesis and its subcellular localization. Previously, we discovered that Aspergillus fumigatus compartmentalizes melanization in endosomes by recruiting all melanin enzymes to the secretory pathway. Surprisingly, although two laccases involved in the late steps of melanization are conventional secretory proteins, the four enzymes involved in the early steps of melanization lack a signal peptide or a transmembrane domain and are thus considered “atypical” secretory proteins. In this work, we found interactions among melanin enzymes and all melanin enzymes formed protein complexes. Surprisingly, the formation of protein complexes by melanin enzymes was not critical for their trafficking to the endosomal system. By palmitoylation profiling and biochemical analyses, we discovered that all four early melanin enzymes were strongly palmitoylated during conidiation. However, only the polyketide synthase (PKS) Alb1 was strongly palmitoylated during both vegetative hyphal growth and conidiation when constitutively expressed alone. This posttranslational lipid modification correlates the endosomal localization of all early melanin enzymes. Intriguingly, bioinformatic analyses predict that palmitoylation is a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Our findings indicate that protein-protein interactions facilitate melanization by metabolic channeling, while posttranslational lipid modifications help recruit the atypical enzymes to the secretory pathway, which is critical for compartmentalization of secondary metabolism. IMPORTANCE Subcellular compartmentalization is increasingly recognized as an important aspect of fungal secondary metabolism. It facilitates sequential enzymatic reactions, provides mobility for enzymes and metabolites, and offers protection against self-toxification. However, how compartmentalization is achieved remains unclear given that the majority of enzymes encoded by secondary metabolism gene clusters are predicted to be cytosolic proteins. Through studying melanization in Aspergillus, we previously found that all enzymes involved in the early steps of melanization are atypical secretory proteins. Here, we discovered physical interactions among melanin enzymes. However, it was the posttranslational palmitoylation rather than the physical interaction that was responsible for their recruitment to the secretory pathway. Intriguingly, palmitoylation is likely a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Collectively, our findings suggest that posttranslational lipid modification helps direct secondary metabolism to defined organelles for biosynthesis and trafficking.Srijana UpadhyayXinping XuXiaorong LinAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 7, Iss 6 (2016)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Srijana Upadhyay Xinping Xu Xiaorong Lin Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
description	ABSTRACT Melanins are biopolymers that confer coloration and protection to the host organism against biotic or abiotic insults. The level of protection offered by melanin depends on its biosynthesis and its subcellular localization. Previously, we discovered that Aspergillus fumigatus compartmentalizes melanization in endosomes by recruiting all melanin enzymes to the secretory pathway. Surprisingly, although two laccases involved in the late steps of melanization are conventional secretory proteins, the four enzymes involved in the early steps of melanization lack a signal peptide or a transmembrane domain and are thus considered “atypical” secretory proteins. In this work, we found interactions among melanin enzymes and all melanin enzymes formed protein complexes. Surprisingly, the formation of protein complexes by melanin enzymes was not critical for their trafficking to the endosomal system. By palmitoylation profiling and biochemical analyses, we discovered that all four early melanin enzymes were strongly palmitoylated during conidiation. However, only the polyketide synthase (PKS) Alb1 was strongly palmitoylated during both vegetative hyphal growth and conidiation when constitutively expressed alone. This posttranslational lipid modification correlates the endosomal localization of all early melanin enzymes. Intriguingly, bioinformatic analyses predict that palmitoylation is a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Our findings indicate that protein-protein interactions facilitate melanization by metabolic channeling, while posttranslational lipid modifications help recruit the atypical enzymes to the secretory pathway, which is critical for compartmentalization of secondary metabolism. IMPORTANCE Subcellular compartmentalization is increasingly recognized as an important aspect of fungal secondary metabolism. It facilitates sequential enzymatic reactions, provides mobility for enzymes and metabolites, and offers protection against self-toxification. However, how compartmentalization is achieved remains unclear given that the majority of enzymes encoded by secondary metabolism gene clusters are predicted to be cytosolic proteins. Through studying melanization in Aspergillus, we previously found that all enzymes involved in the early steps of melanization are atypical secretory proteins. Here, we discovered physical interactions among melanin enzymes. However, it was the posttranslational palmitoylation rather than the physical interaction that was responsible for their recruitment to the secretory pathway. Intriguingly, palmitoylation is likely a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Collectively, our findings suggest that posttranslational lipid modification helps direct secondary metabolism to defined organelles for biosynthesis and trafficking.
format	article
author	Srijana Upadhyay Xinping Xu Xiaorong Lin
author_facet	Srijana Upadhyay Xinping Xu Xiaorong Lin
author_sort	Srijana Upadhyay
title	Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
title_short	Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
title_full	Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
title_fullStr	Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
title_full_unstemmed	Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation
title_sort	interactions between melanin enzymes and their atypical recruitment to the secretory pathway by palmitoylation
publisher	American Society for Microbiology
publishDate	2016
url	https://doaj.org/article/8bd9292c7398484781d81a7e3526b605
work_keys_str_mv	AT srijanaupadhyay interactionsbetweenmelaninenzymesandtheiratypicalrecruitmenttothesecretorypathwaybypalmitoylation AT xinpingxu interactionsbetweenmelaninenzymesandtheiratypicalrecruitmenttothesecretorypathwaybypalmitoylation AT xiaoronglin interactionsbetweenmelaninenzymesandtheiratypicalrecruitmenttothesecretorypathwaybypalmitoylation
_version_	1718427471508930560

Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation

Ejemplares similares